Investigation of the Stationary and Transient A1·− Radical in Trp → Phe Mutants of Photosystem I

Photosystem I (PS I) contains two symmetric branches of electron transfer cofactors. In both the A- and B-branches, the phylloquinone in the A1 site is π-stacked with a tryptophan residue and is H-bonded to the backbone nitrogen of a leucine residue. In this work, we use optical and electron paramagnetic resonance (EPR) spectroscopies to investigate cyanobacterial PS I complexes, where these tryptophan residues are changed to phenylalanine. The time-resolved optical data show that backward electron transfer from the terminal electron acceptors to P700·+ is affected in the A- and B-branch mutants, both at ambient and cryogenic temperatures. These results suggest that the quinones in both branches take part in electron transport at all temperatures. The electron-nuclear double resonance (ENDOR) spectra of the spin-correlated radical pair P700·+A1·− and the photoaccumulated radical anion A1·−, recorded at cryogenic temperature, allowed the identification of characteristic resonances belonging to protons of the methyl group, some of the ring protons and the proton hydrogen-bonded to phylloquinone in the wild type and both mutants. Significant changes in PS I isolated from the A-branch mutant are detected, while PS I isolated from the B-branch mutant shows the spectral characteristics of wild-type PS I. A possible short-lived B-branch radical pair cannot be detected by EPR due to the available time resolution; therefore, only the A-branch quinone is observed under conditions typically employed for EPR and ENDOR spectroscopies

Women’s acceptability of screening for HIV in pregnancy

Aims. To elicit acceptability of HIV screening during pregnancy in women of reproductive age in Christchurch. Methods. In-depth face-to-face interviews were conducted with women of reproductive age recruited from seven different service sites in Christchurch. Results. Women wanted to know about treatment that significantly reduces the risk of mother-to-child transmission. They wanted to know about other antenatal screening and were prepared to provide general consent, rather than specific consent for HIV testing. All study participants favoured routine offer of HIV testing during pregnancy for all women and most would agree to be tested, if the test was offered and recommended. Conclusions. The results of this study indicate the need to develop and test a user-friendly approach for offering routine HIV testing during standard antenatal care in New Zealand